It is important to measure thermal distribution characteristics of micro devices, such as semiconductor devices, photoelectric devices, or the like, so as to evaluate and improve performances of the devices. According to a known non-contact thermo-distribution measuring method, there has been an infrared thermography technique, in which the infrared radiation emitted from a sample is directly measured using an infrared camera. The infrared thermography technique has a spatial resolving power of about 3 um, due to a diffraction limit caused by middle range infrared radiation used to form a temperature image, while the infrared thermography technique can realize a high temperature resolving power of about 10 mK to 20 mK. Thus, in order to realize a high spatial resolving power of less than 1 um, it is necessary to use a short wavelength light. Because of these reason, various thermo-reflectance techniques have been reported to use a visible or ultraviolet range wavelength light. According to the techniques, the short wavelength lights in an ultraviolet or visible light band illuminate a sample and a relative reflectance change depending on a temperature change is measured so that the temperature distribution of the sample can be extracted. One of the techniques is depicted in M. Farzanech et. al. J. Phys. D. vol. 42, p.143001, 2009. In this paper, since light having a wavelength of less than 500 nm is used in the technique, the technique has an advantage that a high spatial resolving power of about 250 nm can be realized, and a temperature resolving power of about 10 mK can also be realized. However, the proposed technique is limited to measuring a temperature distribution on a two-dimensional surface.
U.S. Patent Application No. 2009/0084959 discloses thermo-reflectance thermography using a confocal microscope based on a Nipkow disk. The invention relates to a technique for measuring a temperature distribution of a device which has a three-dimensional structure packaged in a transparent material.
According to U.S. Patent Application No. 2009/0084959, a two-dimensional temperature distribution in a focal region can be measured with a high spatial resolving power using a thermo-reflectance technique. However, the method has a disadvantage that a sample or a lens system needs to be moved in a depth direction so as to perform three-dimensional measurement.
Thus, the mechanical vibration which is caused by movement of the sample or system is one factor of errors in temperature measurement. Furthermore, since the sample or a measurement system is moved in a vertical direction, a long measurement time is an obstacle of a real-time three-dimensional temperature distribution measurement.